#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
int main()
{
    int n, x, y;
    int m = -1;
    scanf("%d %d %d", &n, &x, &y);
    if (y <= n * x)
    {
        if (y % x > 0)
            m = n - (y / x + 1);
        else
            m = n - (y / x);
    }
    printf("%d", m);
    return 0;
}
